Use of emulsions in dewaxing oil



Dec. 27, 1955 R. A. MACKE ETAL 2,723,709

USE OF EMULSIONS IN DEWAXING OIL Filed Sept. 8, 1952 l4 /O H I Warm Warms y Dewaxing Solvent Wafer Solvent lncorporafor Emulsifier' lncorporaforChilling To Dewaxing Temperafure Separation Of Solids From LiquidDewaxed Wax Oil IN V EN TORS Robert A Mac/(e y Winfred 0. illi an 299/7" ATTORNEY United States Patent USE on EMULSIONS 1N DEWAXING on.

Application September 8, 1952, Serial No. 308,325

4 Claims. (Cl. 196-18) The present invention is directed to a method forsolvent dewaxing lubricating oil.

It is well known to the art to remove wax from a waxy oil by dissolvingthe waxy oil in solvent, chilling the resultant solution to cause thewax to precipitate and then separating the precipitated wax by somesuitable means such as filtration or gravity settling. The presentapplication is directed to an improved method for solvent dewaxing oil.

The practice of the present invention will now be described in detail inconjunction with the accompanying drawing in which:

The sole figure is in the form of a flow sheet.

In the practice of the present invention an emulsion of the water-in-oiltype is formed in which the water is dispersed to such an extent that atleast 90% is within the particle size range of 5 to microns.

Warm waxy oil is dissolved in solvent at a temperature above the waxnucleation temperature and emulsion is then incorporated therein in suchan amount that the finely dispersed water droplets are present in thewaxy oil in an amount within the range of .25 to 5% by volume. Theresultant solution containing the finely dispersed water droplets isthen cooled to the desired dewaxing temperature which causes theseparation of wax particles in the form of large agglomerates therebyallowing the ready separation of the wax phase from a wax tree oilphase.

The important features of the procedure arethe forming of a separatewater-in-oil type of emulsion which is incorporated in the solution ofwaxy oil dissolved in solvent at a temperature above the wax nucleationtemperature under such conditions that the finely dispersed waterparticles pass into the waxy oil and remain therein while the waxy oilis chilled to a temperature below the wax nucleation temperature. Asstated heretofore, in the practice of the present invention the finelydispersed water present in the waxy oil at the wax nucleationtemperature may be within the range of .25 to 5% by volume andsatisfactory results will be obtained. With a lubricating oil feed stockcontaining wax within the range of 5 to by volume it will often be foundthat when the free water at the wax nucleation temperature is within therange of .25 to 1.10% by volume the most satisfactory results aresecured. It may be found when separating oil from wax mixtures where thewax is present in considerably greater amounts, for example over thatlarger amounts of water in finely dispersed form, up to 5% by volume atthe wax nucleation temperature may give the most desirable results.

It is essential that the water added in the form of a water-in-oil typeemulsion remain as finely divided particles dispersed in the waxy oilsolution as the solution is chilled to below the wax nucleationtemperature. Thus a solvent must be employed which will not cause thefinely divided particles to coalesce before such a chilling can becarried out. It will usually be found desirable to 2,728,709 PatentedDec. 27, 1955 employ a solvent which has a low solubility for water. Apreferred solvent is propane. However, the invention is not limited topropane since other solvents having a low solubility for water are wellknown to the art. Examples of other suitable solvents known to the artto have a low solubility for water are naphtha, high molecular weightalcohols such as amyl alcohol, a ketone-light aromatic hydrocarbonmixture, and chlorinated solvents such as ethylene dichloride benzolmixture, ethylene dichloride, carbon tetrachloride mixture andtrichloroethylene. It may be possible to employ solvents or solventmixtures having considerable water solubility by first saturating themwith water but ordinarily this is not desirable. In general, if thesolvent is capable of dissolving a considerable amount of water it willbe preferable to dissolve the water in the solvent at a high temperatureand then cool down to separate out the water in finely divided form asdisclosed and claimed in the copending U. S. Patent application SerialNo. 308,323, entitled Solvent Dewaxing of Lubricating Oil filed in thename of Robert A. Macke on September 8, 1952, while the presentinvention where finely divided water particles are obtained in the waxyoil solution by adding an emulsion thereto is particularlv advantageousin cases Where the solvent has a low water solubility.

Turning now specifically to the drawing which is in the form of a flowsheet, water from 10 and solvent from 11 are mixed together with oilfrom 15 introduced by valve-controlled line 9 to form an emulsion inemulsifier 12. Warm dewaxing solvent from 14 is used to dissolve warmwaxy oil from 15, the two fractions being mixed in incorporator 16 toform a solution. The resultant solution has incorporated therein inincorporator 17 emulsion from emulsifier 12. The resultant solution ofwaxy oil has therein dispersed water particles in an amount within therange of .25 to 5% by volume with approximately 90% in the size range of5 to 20 microns and is then chilled in 13 to a selected dewaxingtemperature. It is to be emphasized that in the chilling step the finelydi vided water particles must be present as the waxy oil is chilled downthrough the wax nucleation temperature. The procedure followed causesthe separation of wax particles in the form of agglomerates which arereadily separated. The solution which has been chilled to the dewaxingtemperature is then separated in separation step 19, such as filteringby means of rotary filter to obtain as products a dewaxed oil fractionand a wax fraction. The drawing is in the form of a flow sheet and itwill be understood that various well known steps such as the recovery ofsolvent from the dewaxed oil and the separated wax have been omitted forthe purpose of simplifying the description.

The present invention will be further described by way of the followingexample:

Example A very tight emulsion was formed by admixing 82 parts by volumeof water, 18 parts by volume of methyl ethyl ketone and 300 parts byvolume of oil in a Waring blendor for 30 seconds. A waxy distillatemotor oil having a viscosity of 53.2 Saybolt seconds at 210 F. wasdivided into first, second and third samples. The wax nucleationtemperature of the motor oil was approximately 115 F. To parts by volumeof each of the samples there was added 100 parts of a solvent mixtureconsisting of a 68% by volume of methyl ethyl ketone, 32% by volume oftoluol solvent mixture containing 0.55% by volume of water at atemperature above the wax nucleation temperature so that each of thesamples was dissolved in solvent mixture. No emulsion was added to thefirst sample. Emulsion was added in the amount of 3.1% by volume to thesecond sample and I an amount of 6.2% by volume in the third sample.Each of the samples was then chilled to approximately F. and filtered.The first sample gave a dewaxed oil filter rate of 11.6 gallons persquare foot per hour, the second sample gave a dewaxed oil filter rateof 14.2 gallons per square foot per hour or an increase of 22% over thefirst sample. The third sample gave a dewaxed oil filter rate of 12.8gallons per square foot per hour or an increase of These results aretabulated in Table I set out hereafter. The first run where no emulsionwas added produced a wax cake having 27% by volume of oil in wax, thesecond run produced a wax cake having 32% oil in Wax, an increase byvolume in oil, While the third run produced a wax cake having 24% byvolume of oil in wax or a decrease of 11% Table l Solvent Composition:

68% by volume methyl ethyl ketone 32% by volume toluol 0.55% by volumewater added 1 82 parts water; 18 parts methyl ethyl ketone; 300 partsoil.

It is not understood why the procedure of the present invention causesthe substantial improvement in results which are obtained. One postulatewhich has been advanced in explanation of the advantageous results isthat the free Water droplets act as nuclei upon which the wax crystalsform and in this Way the actual number of nuclei formed are controlledand thereby control the size of the resultant wax crystals. Anotherpostulate which has been proposed is that each finely divided particleof water serves as a body, upon the interface of which wax nucleicollect thereby causing a large wax agglomerate to form. In the art offiltration it is known that larger crystals or larger crystalagglomerates filter more rapidly than small crystals and thus either ofthe postulates advanced would result in a more rapid filtration rate. Inany event the procedure of the present invention does result insubstantially improved filtration rates.

We claim:

1. A method of dewaxing a waxy mineral oil including the steps ofincorporating into a solution of Waxy mineral oil and dewaxing solventat a temperature above the wax nucleation temperature, a water-in-oiltype of emulsion formed by admixing solvent, oil, and water in which atleast 90% of the Water is within the particle size range of 5 to 20microns in an amount such that the finely dispersed water particles arepresent and remain in the solution in an amount within the range of 0.25to 5% by volume based on the solution at a wax nucleation temperature,chilling the resultant solution containing said finely dispersed waterparticles to a temperature substantially below the wax nucleationtemperature to cause wax crystals to form while said dispersion waterparticles are present and subsequently separating a wax crystal fractionfrom a wax free oil fraction.

2. A method of dewaxing a Waxy mineral oil containing wax within therange of 5 to 25% by volume including the steps of dissolving said waxymineral oil at a temperature above the wax nucleation temperature in asolvent having a low water solubility, adding to the solution awater-in-oil type of emulsion formed by admixing solvent, oil, andwater, and having the water dispersed so that at least is within theparticle size range of 5 to 20 microns in an amount within the range of.25 to 1.10% by volume based on the solution at a wax nucleationtemperature, chilling the waxy oil solution containing said finelydispersed particles of water to a temperature substantially below thewax nucleation temperature to cause wax crystals to form in the presenceof said dispersed particles of water and subsequently separating a waxcrystal fraction from a wax free oil fraction.

3. A method for dewaxing a waxy mineral oil containing wax within therange of 5 to 25% by volume which includes the steps of dissolving saidwaxy mineral oil at a temperature above the wax nucleation temperaturein propane, forming a water-in-oil type of emulsion by admixing methylethyl .ketone, oil and water with the water dispersed so that at least90% is Within the particle size range of 5 to 20 microns, adding saidemulsion to said solution of waxy oil in an amount to incorporate from.25 to 5% by volume based on the solution at wax nucleation temperatureof finely dispersed water in said solution of waxy oil, chilling saidwaxy oil solution containing said finely dispersed Water particles to atemperature substantially below the wax nucleation temperature to causewax crystals to form in the presence of said dispersed Water particlesand subsequently separating a wax crystal fraction from a wax free oilfraction.

4. A method in accordance with claim 3 in which said emulsion is formedby mixing approximately 82 parts by volume of water, 18 parts by volumeof methyl ethyl ketone and 300 parts by volume of oil.

References Cited in the file of this patent UNITED STATES PATENTS2,164,013 Jenkins June 27, 1939 2,263,535 Carr et a1. Nov. 18, 19412,478,456 Boudreaux et a1. Aug. 9, 1949 2,584,966 Reeves Feb. 5, 19522,645,597 Myers et a1. July 14, 1953 2,674,565 Myers Apr. 6, 19542,688,587 Pokorny et al. Sept. 7, 1954

1. A METHOD OF DEWAXING A WAXY MINERAL OIL INCLUDING THE STEPS OFINCORPORATING INTO A SOLUTION OF WAXY MINERAL OIL DEWAXING SOLVENT AT ATEMPERATURE ABOVE THE WAX NUCLEATION TEMPERATURE, A WATER-IN-OIL TYPE OFEMULSION FORMED BY ADMIXING SOLVENT, OIL AND WATER IN WHICH AT LEAST 90%OF THE WATER IS WITHIN THE PARTICLE SIZE RANGE OF 5 TO 20 MICRONS IN ANAMOUNT SUCH THAT THE FINELY DISPERSED WATER PARTICLES ARE PRESENT ANDREMAIN IN THE SOLUTION IN AN AMOUNT WITHIN THE RANGE OF 0.25 TO 5% BYVOLUME BASED ON THE SOLUTION AT A WAX NUCLEATION TEMPERATURE, CHILLINGTHE RESULTANT SOLUTION CONTAINING SAID FINELY DISPERSED WATER PARTICLESTO A TEMPERATURE SUBSTANTIALLY BELOW THE WAX NUCLEATION TEMPERATURE TOCAUSE WAX CRYSTALS TO FORM WHILE SAID DISPERSION WATER PARTICLES AREPRESENT AND SUBSEQUENTLY SEPARATING A WAX CRYSTAL FRACTION FROM A WAXFREE OIL FRACTION.